A common implementation of a system is to have specialized components which are built in a cost effective manner that are combined together to form a system that performs a set of functions. In most video processing systems such as a set-top box, there is a main processing unit, such as system on chip, and external memory devices, in addition to various interface and support devices. The external memory is often used to store temporary data required by the system in order to achieve the function. In the case of a video processing system, external memory is often used to hold video images before they are displayed.
A common problem with the implementation of the system is that the interface between the main processing unit, the system on chip, and the external memory has a limited bandwidth. In general, the smaller the number of pins an interface requires, the cheaper it is to manufacture. Technology and speed also play a large part in the performance, but often these are limited by the memory technologies available in volume quantities, such as dynamic random-access memory devices.